Swash plate-type compressors

ABSTRACT

A swash plate-type compressor includes a housing having a cylinder block with a plurality of cylinder bores formed therethrough. The cylinder block encloses a crank chamber, a suction chamber, and a discharge chamber. The compressor also includes a drive shaft rotatably supported by the housing, a plurality of pistons positioned within a corresponding one of the cylinder bores, and a swash plate rotatably mounted on the drive shaft. The compressor further includes a discharge path formed between the crank chamber and the suction chamber. Moreover, the compressor includes a check valve positioned within the discharge path. The check valve is adapted to open the discharge path when a first pressure in the crank chamber is greater than a second pressure in the suction chamber and to close the discharge path when the first pressure is less than or equal to the second pressure. Consequently, a refrigerant within the crank chamber is discharged into the suction chamber when the first pressure is greater than the second pressure. Nevertheless, the refrigerant within the suction chamber is not discharged into the crank chamber when the first pressure is less than or equal to the second pressure.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to swash plate-typecompressors used in automotive air conditioning systems. In particular,the present invention is directed towards swash plate-type compressorshaving a discharge path between a crank chamber and a suction chamber,and a check valve for opening and closing the discharge path based onthe pressure in the crank chamber and the suction chamber, respectively.

[0003] 2. Description of Related Art

[0004] Known swash plate-type compressors include a cylinder block, afront housing, a valve plate, and a cylinder head. The cylinder block issubstantially cylindrical, and also is enclosed by the front housing andthe cylinder head. Such known compressors also include a crank chamberformed between the cylinder block and the front housing, and a suctionchamber and a discharge chamber formed within the cylinder head adjacentto the value plate. Moreover, such known compressors include an inletport and an outlet port adapted to communicate with the suction chamberand the discharge chamber, respectively. The inlet port and the outletport are connected to a refrigerant circuit of an air conditioningsystem of a vehicle. The cylinder block, the front housing, the valveplate, and the cylinder head are attached fixably to each other by aplurality of bolts. Such known compressors further include a pluralityof cylinder bores formed in the cylinder block, and the cylinder boresare arranged radially with respect to a central axis of the cylinderblock.

[0005] Such known compressors also include a drive shaft, a swash plate,a plurality of shoes, and a plurality of pistons. The drive shaftextends along a central axis of the compressor through the crankchamber, and also is supported rotatably by the front housing and thecylinder block via a pair of bearings mounted in the front housing andthe cylinder block, respectively. Such known compressors also include anelectromagnetic clutch, and a drive belt is used to engage theelectromagnetic clutch by transmitting a drive force from a crankshaftof an engine of the vehicle to the electromagnetic clutch. When theelectromagnetic clutch is engaged, the driving force also is transmittedfrom the electromagnetic clutch to the drive shaft. Moreover, the swashplate is positioned within the crank chamber, and is mounted slidably onthe draft shaft, such that an inclination angle of the swash platevaries relative to a radial line which extends perpendicular to thedrive shaft.

[0006] Moreover, each piston is positioned within a correspondingcylinder bore, and the pistons reciprocate independently within theircorresponding cylinder bore. Each of the pistons also is connected tothe swash plate via a pair of shoes. In such known compressors, adischarge path is adapted to provide fluid communication between thecrank chamber and the suction chamber. When a refrigerant is compressed,the refrigerant leaks into the crank chamber via a clearance betweeneach piston and their corresponding cylinder bore, and accumulateswithin the crank chamber. Moreover, the accumulated refrigerantsubsequently is discharged into the suction chamber.

[0007] Nevertheless, when such known compressors are not in operation,and a temperature of an evaporator or a condenser in the refrigerantcircuit is greater than a temperature of the compressor, the refrigerantflows into the crank chamber from the suction chamber via the dischargepath. Similarly, when a pressure in the suction chamber is greater thana pressure in,the crank chamber, and a temperature of refrigerant in theevaporator or the condenser is greater than a saturated temperature ofthe refrigerant, the refrigerant flows into the crank chamber from thesuction chamber via the discharge path, the refrigerant cools into aliquid which accumulates in the crank chamber. Subsequently, when theoperation of the compressor begins, lubricant oil, which is on a surfaceof the swash plate and a surface of each piston, is washed away by theliquid refrigerant accumulated in the crank chamber, and the lubricantoil and the liquid refrigerant are discharged from the crank chamberinto the suction chamber via the discharge path. Thus, an amount oflubricant oil at a sliding portion between an exterior surface of theswash plate and an exterior surface of each shoe, and an amount oflubricant oil at a sliding portion between an exterior surface of eachpiston and an interior surface of their corresponding cylinder bores,are reduced. Consequently, an amount of friction at the sliding portionbetween the swash plate and the shoes and an amount of friction at thesliding portion between the pistons and their corresponding cylinderbores increase.

SUMMARY OF THE INVENTION

[0008] Therefore, a need has arisen for swash plate-type compressorswhich overcome these and other shortcomings of the related art. Atechnical advantage of the present invention is that when a swashplate-type compressor is not in operation, a liquid refrigerant does notaccumulate in the crank chamber of the compressor.

[0009] According to an embodiment of the present invention, a swashplate-type compressor is described. The swash plate-type compressorcomprises a housing having a cylinder block with a plurality of cylinderbores formed therethrough. The cylinder block encloses a crank chamber,a suction chamber, and a discharge chamber. The compressor alsocomprises a drive shaft rotatably supported by the housing; a pluralityof pistons each of which is positioned within a corresponding one of thecylinder bores, and a swash plate rotatably mounted on the drive shaft.The compressor further comprises a discharge path formed between thecrank chamber and the suction chamber. Moreover, the compressorcomprises a check valve positioned within the discharge path. The checkvalve is adapted to open the discharge path when a first pressure in thecrank chamber is greater than a second pressure in the suction chamber,and to close the discharge path when the first pressure is less than orequal to the second pressure. Consequently, a refrigerant within thecrank chamber is discharged into the suction chamber via the dischargepath when the first pressure is greater than the second pressure.Nevertheless, the refrigerant within the suction chamber is notdischarged back into the crank chamber when the first pressure is lessthan or equal to the second pressure.

[0010] Other objects, features, and advantages of the present inventionwill be apparent to persons of ordinary skill in the art in view of theforegoing detailed description of the invention and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a more complete understanding of the present invention, needssatisfied thereby, and the objects, features, and advantages thereof,reference now is made to the following description taken in connectionwith the accompanying drawings.

[0012]FIG. 1 is a cross-sectional view of a swash plate-type compressor,according to an embodiment of the present invention.

[0013]FIG. 2 is a partial, enlarged cross-sectional view of thecompressor of FIG. 1.

[0014]FIG. 3 is a cross-sectional view of a swash plate-type compressor,according to another embodiment of the present invention.

[0015]FIG. 4 is a partial, enlarged cross-sectional view of a swashplate-type compressor, according to yet another embodiment of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0016] Preferred embodiments of the present invention, and theirfeatures and advantages, may be understood by referring to FIGS. 1-4,like numerals being used for corresponding parts in the variousdrawings.

[0017] Referring to FIGS. 1 and 2, a swash plate-type compressor 100according to an embodiment of the present invention is depicted. Asshown in FIG. 1, compressor 100 may comprise a cylinder block 1, a fronthousing 2, a valve plate 6, and a cylinder head 4. Cylinder block 1 maybe substantially cylindrical and also may be enclosed by front housing 2and cylinder head 4. Compressor 100 also may comprise a crank chamber 3formed between cylinder block 1 and front housing 2. Moreover,compressor 100 may comprise a suction chamber 8 and a discharge chamber9 formed within cylinder head 8 adjacent to valve plate 6. Compressor100 further may comprise an inlet port (not shown) and an outlet port(not shown), which may be adapted to communicate with suction chamber 8and discharge chamber 9, respectively. The inlet port and the outletport may be connected to a refrigerant circuit (not shown) of an airconditioning system of a vehicle. Cylinder block 1, front housing 2,valve plate 6, and cylinder head 4 may be fixable attached to each otherby a plurality of bolts 50. Compressor 100 also may comprise a pluralityof cylinder bores 1 a formed in cylinder block 1, and cylinder bores 1 amay be arranged radially with respect to a central axis of cylinderblock 1.

[0018] Compressor 100 further may comprise a drive shaft 10, a swashplate 11, a plurality of shoe pairs 12, and a plurality of pistons 13.Drive shaft 10 may extend along a central axis of compressor 100 throughcrank chamber 3. Drive shaft 10 also may be supported rotatably by fronthousing 2 via a bearing 20 a mounted in front housing 2, and by cylinderblock 1 via a plurality of bearings 20 b mounted in a center bore 1 bformed at a center of cylinder block 1. Swash plate 11 may be positionedwithin crank chamber 3, and may be mounted fixedly on drive shaft 10.Each shoe 12 may engage a sliding surface of swash plate 11, and may bein slidable contact with the sliding surface of swash plate 11. Shoes 12may be positioned radially in a circumferential direction at a regularinterval with respect to each other. Each pair of shoes 12 also mayengage slidably one of piston 13. As such, each piston 13 may be incontact with swash plate 11 via one pair of shoes 12. Moreover, eachpiston 13 may be positioned within a corresponding cylinder bore 1 a andmay reciprocate independently within corresponding cylinder bore 1 a.

[0019] Center bore 1 b of cylinder block 1 may be in communication withsuction chamber 8 via a refrigerant path (not shown), and a dischargepath comprises center bore 1 b and the refrigerant path. When arefrigerant is compressed, the refrigerant may leak into crank chamber 3via a sliding portion between an exterior surface of piston 13 and aninterior surface of cylinder bore 1 a.

[0020] A check valve 14 may be positioned within center bore 1 b. Asshown in FIG. 2, check valve 14 may comprise a case 14a having acylindrical shape and a bottom wall 14 k. Case 14 a may be fitted withcenter bore 1 b, and a contact portion between case 14 a and center bore1 b may be sealed by an O-ring 14 b. A plurality of openings 14 cadapted to lock an annular valve seat 14 d may be formed through aflange, and the flange may be formed at an open end 14 j of case 14 a.Valve seat 14 d may contact open end 14 j of case 14 a when a pluralityof hooks 14 d′ of valve seat 14 d are inserted inside the plurality ofopenings 14 c of case 14 a. A plurality of vents 14 e may be formedthrough bottom wall 14 k of case 14 a, and a spring 14 f may bepositioned within case 14 a. A valve element 14 g may be fixed to an endof spring 14 f at a side of crank chamber 3, and a plurality of supports14 h may extend from case 14 a toward suction chamber 8.

[0021] When compressor 100 is in operation, drive shaft 10 may rotatevia an external power source, e.g., an engine of a vehicle, and swashplate 11 may rotate substantially simultaneously with drive shaft 10about an axis of drive shaft 10. When swash plate 11 rotates, eachpiston 13 may reciprocate within their corresponding cylinder bores 1 a.When pistons 13 reciprocate within their corresponding cylinder bores 1a, refrigerant, which is introduced into suction chamber 8 via the inletport, may be drawn into each cylinder bore 1 a via suction ports 5, andthe refrigerant subsequently may be compressed by pistons 13. When therefrigerant is compressed, a discharge reed valve 7 a may open, and therefrigerant may be discharged from cylinder bores 1 a into dischargechamber 9 via a discharge port 7 b formed through a valve plate 6.Moreover, the refrigerant then may be discharged from discharge chamber9 into the refrigerant circuit via the outlet port.

[0022] Nevertheless, as described above, when compressor 100 is inoperation, refrigerant may leak into crank chamber 3 via the slidingportion between each piston 13 and their corresponding cylinder bores 1a. Moreover, during operation, or after the operation of compressor 100stops, if a pressure Pc in crank chamber 3 is greater than a pressure Psin suction chamber 8, valve element 14 g moves away from valve seat 14d. When valve element 14 g moves away from valve seat 14 d, thedischarge path comprising center bore 1 b and the refrigerant pathopens. As such, the refrigerant in crank chamber 3 may be dischargedinto suction chamber 8 via the discharge path. Because supports 14 h maybe in contact with valve plate 6, however, a plurality of vents 14 eformed through the bottom wall of case 14 a may remain open when valveelement 14 g moves away from valve seat 14 d. In contrast, if thepressure Pc in crank chamber 3 is less than or equal to the pressure Psin suction chamber 8, valve element 14 g contacts valve seat 14 d, whichcloses the discharge path. Consequently, the refrigerant does not flowfrom suction chamber 8 to crank chamber 3 via the discharge path.

[0023] After the operation of compressor 100 has been stopped for apredetermined period of time, a temperature of an evaporator or acondenser in the refrigerant circuit may become greater than atemperature of compressor 100. Moreover, the pressure Ps in suctionchamber 8 may become greater than the pressure Pc in crank chamber Ps,and a temperature of refrigerant in the evaporator or the condenser maybecome greater than a saturated temperature of the refrigerant. In thiscondition, the discharge path is closed by valve element 14 g of checkvalve 14, and the refrigerant in suction chamber 8 does not flow intocrank chamber 3 via the discharge path. Consequently, a liquidrefrigerant does not accumulate in crank chamber 3, and a lubricant oilon a surface of swash plate 11 and pistons 13 is not washed away by theliquid refrigerant when the operation of compressor 100 begins. As aresult, sufficient lubricant oil may be maintained between an exteriorsurface of swash plate 11 and an exterior surface of shoes 12 which arein sliding contact with each other, and sufficient lubricant oil may bemaintained at the sliding portion between each piston 13 and theircorresponding cylinder bores 1 a. Moreover, an amount of friction at thesliding portion between swash plate 13 and shoes 12, and an amount offriction at the sliding portion between each piston 13 and theircorresponding cylinder bores 1 a, may not increase.

[0024] Referring to FIG. 3 another embodiment of the present inventionis depicted. The features and advantages of this embodiment of thepresent invention are substantially similar to the features andadvantages of the previously described embodiment of the presentinvention. Therefore, the features and advantages of the previouslydescribed embodiment of the present invention are not discussed furtherwith respect to this embodiment of the present invention. In thisembodiment, a check value 24 may have a pillar shape and may bepositioned within center bore 1 b. Check valve 24 may have a penetrationpath 24 a. A first end of penetration path 24 a may open into crankchamber 3, and a second end of penetration path 24 a may open intosuction chamber 8, such that crank chamber 3 and suction chamber 8 maybe in fluid communication via penetration path 24. Check valve 24 maycomprise a valve seat 24 a′, which may have a funnel shape. Valve seat24 a′ may be positioned adjacent to the second end of penetration path24 a. Check valve 24 also may comprise a valve element 24 b which mayhave a substantially circular or spherical shape. Valve element 24 maybe positioned within penetration path 24 a, such that valve element 24 bmay contact valve seat 24 a′. Valve element 24 b may comprise rubber,plastic, or the like. Moreover, an O-ring 24 c may seal a contactportion between check valve 24 and center bore 1 b.

[0025] When the pressure Pc in crank chamber 3 is greater than thepressure Ps in suction chamber 8, valve element 24 b may move away fromvalve seat 24 a′. Subsequently, a discharge path comprising center bore1 b and a refrigerant path (not shown) opens. In contrast, when thepressure Pc in crank chamber 3 is less than or equal to the pressure Psin suction chamber 8, valve element 24 b may contact valve seat 24 a′.Subsequently, the discharge path closes. In a modification of thisembodiment or the previous embodiment, a check valve having a reed valvemay be used instead of check valve 14 and 24, respectively.

[0026] Referring to FIG. 4, yet another embodiment of the presentinvention is depicted. The features and advantages of this embodiment ofthe present invention are substantially similar to the features andadvantages of the previously described embodiments of the presentinvention. Therefore, the features and advantages of the previouslydescribed embodiments of the present invention are not discussed furtherwith respect to this embodiment of the present invention. In thisembodiment, a check valve 34 may be positioned within center bore 1 b.Check valve 34 may have a case 34 a, and case 34 a may have acylindrical shape. A first portion of check vale 34 may be formed at aside of crank chamber 3, and a second portion of check valve 34 may beformed at a side of discharge chamber 9. Moreover, the diameter of thefirst portion may be greater than the diameter of the second portion.The first portion of check valve 34 may be positioned within center bore1 b, and an O-ring 34 b may seal a contact portion between the firstportion of check valve 34 and center bore 1 b. A bottom wall 34 h ofcheck valve 34 may have a vent and may comprise a valve seat 34 c. Aplurality of vents 34 d may be formed through a side wall 34 j of checkvalve 34 at the first portion of check valve 34. A cap 34 e may beelastically engaged with a flange formed at an open end 34 k of checkvalve 34, and a valve element 34 f may be positioned within case 34 a. Aspring 34 g may be positioned between valve element 34 f and cap 34 e.

[0027] When the pressure Pc in crank chamber 3 is greater than pressurePs in suction chamber 8, valve element 34 f moves away from valve seat34 c. Subsequently, a discharge path comprising center bore 1 b and arefrigerant path (not shown) may open. As a result, the refrigerant incrank chamber 3 may be discharged into suction chamber 8 via thedischarge path. Nevertheless, vents 34 d formed through the secondportion of check valve 34 may remain open when the discharge path isopen. In contrast, if the pressure Pc in crank chamber 3 is less than orequal to the pressure Ps in suction chamber 8, valve element 34 fcontacts valve seat 34 c, and the discharge path is closed.

[0028] While the invention has been described in connection withpreferred embodiments, it will be understood by those of ordinary skillin the art that other variations and modifications of the preferredembodiments described above may be made without departing from the scopeof the invention. Other embodiments will be apparent to those ofordinary skill in the art from a consideration of the specification orpractice of the invention disclosed herein. The specification and thedescribed examples are considered as exemplary only, with the true scopeand spirit of the invention indicated by the following claims.

What is claimed is:
 1. A swash plate-type compressor comprising: ahousing having a cylinder block with a plurality of cylinder boresformed therethrough, wherein the cylinder block encloses a crankchamber, a suction chamber, and a discharge chamber; a drive shaftrotatably supported by the housing; a plurality of pistons each of whichis positioned within a corresponding one of the cylinder bores; a swashplate rotatably mounted on the drive shaft; a discharge path formedbetween the crank chamber and the suction chamber; and a check valvepositioned within the discharge path, wherein the check valve is adaptedto open the discharge path when a first pressure in the crank chamber isgreater than a second pressure in the suction chamber, and to close thedischarge path when the first pressure is less than or equal to thesecond pressure, such that a refrigerant within the crank chamber isdischarged into the suction chamber via the discharge path when thefirst pressure is greater than the second pressure.
 2. The swashplate-type compressor of claim 1, wherein the discharge path comprises acenter bore formed in the cylinder block.
 3. The compressor of claim 1,wherein the check valve comprises: a case having a substantiallycylindrical shape and a bottom portion, wherein at least one firstopening is formed through the bottom portion, a valve seat adapted toclose an open end of the case, wherein a second opening is formedthrough the valve seat; a valve element positioned within the case andfixed to a biasing member; and a plurality of supports extending fromthe bottom portion of the case.
 4. The compressor of claim 1, whereinthe check valve comprises: a penetration path formed through the checkvalve; a valve seat having a substantially funnel-like shape and formedat an end of the penetration path; and a valve element adapted to bereceived by the valve seat.
 5. The compressor of claim 1, wherein thecheck valve comprises: a case having a substantially cylindrical shapeand a bottom portion, wherein a first opening is formed through thebottom portion and at least one second opening is formed through a sidewall of the case, and wherein there is a clearance between the side walland an inner surface of the discharge path; a cap adapted to close anopening of the case; and a valve element positioned within the case andfixed to a biasing member.